FDA核准非鴉片類藥物貼片用於疱疹後神經痛
作者：Yael Waknine
出處：WebMD醫學新聞
November 18, 2009 — 美國食品藥物管理局（FDA）核准了8%辣椒素經皮貼片（Qutenza，Lohmann Therapie系統AD製作，由Neuroges X公司銷售）用於處理疱疹後神經痛（PNH）。
這個非鴉片類藥物不太會造成嗜睡或是藥物交互作用，且每次使用提供超過12週的局部疼痛緩解。每次使用一小時可能最多用到4片，可視需求裁切使用在疼痛區域。
PNH可以是非常痛苦的疼痛，可能對病患的生活品質造成諸多影響。猶他州鹽湖市Lifetree臨床研究醫療主任Lynn Webster醫師在公司的一篇新聞稿中表示，雖然有許多藥物可以處理疼痛，但副作用的不適經常限制了這些藥物的使用，因此，PNH治療代表著顯著的需求。Qutenza可能提供一種獨特的選擇，可以作用在疼痛位置，且可能作為與其他現存治療合併的治療選擇。
這個藥物的核准案是根據兩項為期12週的第三期臨床研究（共收納818位病患），這些罹患PNH病患接受1小時0.8%（640 μg/cm2）的辣椒素貼片，或是低濃度（3.2 μg/cm2）版本；所有病患都接受到最高表面積1000 cm2的藥物。
這兩項研究結果顯示，使用高濃度辣椒素貼片，從試驗前到8週後，以11分數字疼痛評分指標的疼痛程度顯著下降（第一項研究-29%±2%相較於-18%±2%；第二項研究-33%±2%相較於-26%±2%）。
兩項研究中最常報告的不良反應為紅腫、疼痛、搔癢與使用時或是使用後短時間內產生的丘疹。FDA建議治療前使用局部外用麻醉藥物。在貼與使用後的急性疼痛應以局部冰敷以及/或是止痛藥物處理。
使用8%辣椒素貼片的受試者，大約1%因為不良反應，包括使用部位疼痛、與血壓升高而停止試驗。
雖然某些病患的血壓上升在撕下貼片後仍持續，但血壓變化平均少於10 mmHg。於每次使用貼片後應仔細觀察血壓至少一個小時，而當治療不穩定或是血壓控制不佳、或最近有心血管或腦血管事件患者時，應該特別注意。
為了避免眼睛或黏膜暴露，8%辣椒素貼片不應該用在臉部或頭部。應以滾動的方式移除貼片，以避免辣椒素氣化。
8%的辣椒素貼片過去由FDA以孤兒藥的形式核准用於PNH治療。其他可能的應用目前正在研究中，包括HIV遠端感覺性多神經病變、以及糖尿病神經病變。
FDA Approves Nonnarcotic Pain Patch for Postherpatic Neuralgia
By Yael Waknine
Medscape Medical News
November 18, 2009 — The US Food and Drug Administration (FDA) has approved an 8% capsaicin dermal patch (Qutenza, made by Lohmann Therapie-Systems AD, marketed by NeurogesX, Inc) for the management of pain associated with postherpatic neuralgia (PHN).
The nonnarcotic product is unlikely to cause drowsiness or drug interactions and provides up to 12 weeks of localized pain relief per application. Each 1-hour session may involve up to 4 patches, cut as needed to conform to the painful area.
"PHN can be an excruciatingly painful condition that can affect many aspects of a patient's quality of life. Despite a variety of medications for pain, undesirable side effects often limit their use and therefore, the treatment of PHN continues to represent a significant unmet need," said Lynn Webster, MD, medical director at Lifetree Clinical Research in Salt Lake City, Utah, in a company news release. "Qutenza may provide a unique treatment option that works at the site of the pain and may be useful as a treatment option in combination with existing therapies."
The drug's approval was based on data from two 12-week, phase 3 clinical trials (n = 818) in which patients with PHN received a single 1-hour application of the 0.8% (640 μg/cm2) capsaicin patch or a low-concentration (3.2 μg/cm2) version; all patches were applied over a maximal surface area of 1000 cm2.
Results from both studies showed that use of the high-concentration capsaicin patch yielded significantly greater reductions in pain intensity from baseline at 8 weeks, as assessed using an 11-point Numeric Pain Rating Scale (study 1, ?29% ± 2% vs ?18% ± 2%; study 2, ?33% ± 2% vs ?26% ± 2%).
Adverse events most commonly reported in both studies included erythema, pain, pruritis, and papules at the application site during and shortly after patch use. The FDA recommends use of a local topical anesthetic before treatment. Acute pain during and after the procedure should be addressed with local cooling and/or analgesics.
Approximately 1% of patients on the 8% capsaicin patch discontinued the study because of adverse events, including application-site pain and associated increases in blood pressure.
Blood pressure changes averaged less than 10 mm Hg, although some patients had greater increases that persisted for about 2 hours after patch removal. Blood pressure should be carefully monitored for 1 hour after each application, and caution is advised when treating patients with unstable or poorly controlled hypertension or a recent history of cardiovascular or cerebrovascular events.
To avoid the risk for exposure of the eyes or mucous membranes, the capsaicin 8% patch should not be applied to the face or scalp. Patches should be removed gently using a rolling motion to avoid capsaicin aerosolization.
Capsaicin 8% patch previously was granted orphan drug status by the FDA in the treatment of PHN. Other potential applications currently under investigation include HIV-distal sensory polyneuropathy and diabetic neuropathy.
